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From: "tom.cosgrove at arm dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/106119] Bogus use-after-free warning triggered by optimizer
Date: Wed, 29 Jun 2022 13:53:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106119

--- Comment #2 from Tom Cosgrove <tom.cosgrove at arm dot com> ---
Further addendum:

If you use a `void *` to save the value of the pointer, you don't get the
warning!

See https://gcc.godbolt.org/z/fof8a747z


i.e. this code does not generate the warning:

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

void calloc_self_test( __attribute__ ((unused)) int verbose )
{
    void *buffer1 =3D calloc( 1, 1 );
    void *old_buffer1 =3D buffer1;
    free( buffer1 );
    buffer1 =3D calloc( 1, 1 );
    int same =3D ( old_buffer1 =3D=3D buffer1 );
    if( verbose )
        printf( "  CALLOC(1 again): passed (%s address)\n",
                same ? "same" : "different" );
    free( buffer1 );
}=